CIS 1200 Lecture Notes - Interjection, Data Warehouse, Query Language

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Published on 15 Apr 2013
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Chapter 11
Chapter Objectives (pg. 508)
What is a database, and why is it beneficial to use databases? (pp. 510
511)
Databases are electronic collections of related data that can be organized so
that it is more easily accessed and manipulated. Properly designed databases
cut down on data redundancy and duplicate data by ensuring relevant data is
recorded in only one place. This also helps eliminate data inconsistency,
which comes from having different data about the same transaction recorded
in two different places. When databases are used, multiple users can share
and access information at the same time. Databases are used any time
complex information needs to be organized or more than one person needs
to access it. In these cases, lists (which are used to keep track of simple
information) are no longer efficient.
What components make up a database? (pp. 512 525)
The three main components of a database are:
1. Fields: A database stores ach category of information in a field, which
is usually displayed in a column (e.g., name)
2. Records: A group of related fields (e.g., name + address + phone)
3. Tables: A group of related records (e.g., all student records)
A category of information in a database is stored in a field. Each field is
identified by a field name, which is a way of describing the field. Fields are
assigned a data type that indicates what type of data can be stored in the
field. Common data types include:
Text field: holds any combination of alphanumeric data
Numeric field: hold numbers that can be used to perform
calculations
Computational field: a field that stores the contents of a
calculation
Date field: holds calendar dates
Memo field: like a text field, but for long pieces of text
Object field: holds items like pictures, videos or documents
Hyperlink field: hold hyperlinks to Web pages
To keep records distinct, each record must have one field that has a value
unique to that record. This unique field is a primary key (or a key field).
What types of databases are there? (pp. 516 517)
The three major types of databases currently in use are:
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1. Relational
Relational databases are characterized by two-dimensional
tables of data in which a common field is maintained in each of
two tables and the information in the tables is linked by this
field.
2. Object-oriented
Object-oriented databases store data in objects, not in tables.
The objects also contain instructions about how the data is to
be manipulated or processed.
3. Multidimensional
Multidimensional databases represent data in three-
dimensional cubes to enable faster retrieval of information
from the database.
What do database management systems do? (pp. 517 526)
Database management systems (DBMSs) are specially designed applications
(such as Oracle or Microsoft Access) that interact with the user, other
applications, and the database itself to capture and analyze data. The main
operations of a DBMS are:
1. Creating databases
Defining the data to be captured by describing it in a “data
dictionary” that defines the name, data type and length of each
field in the database.
2. Entering data
Inputting the data into the database fields. Data is validated by
field constraints, which are properties that must be satisfied
for an entry to be accepted into a field
o Range check: ensures that data falls within a certain
range of numbers
o Field constraint: a property that must be satisfied for
an entry to be accepted into the field
o Completeness check: a field that is required to have
data in it
o Consistency check: compares the value of data in two
or more fields to see if these values are reasonable
o Alphabetic check: confirms that only textual
characters are entered in a field
o Numeric check: confirms that only numbers are
entered in a field
3. Viewing (or browsing) data
Displaying the tables on screen, often with a variety of viewing
options
4. Sorting (or indexing) data
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Organizing the displayed data by a certain field (column) in
either ascending or descending order
5. Extracting (or querying) data
Requesting specific records to be viewed in a query language
(such as SQL)
e.g., requesting records for all students with a date of birth
between 1990 1991)
6. Outputting data
Printable electronic reports (such as a summary of today’s
sales transactions) or exporting data to other applications
A query language is used to extract records from a database. Almost all
relational databases today use structured query language, or SQL. However,
most DBMSs include wizards that enable you to query the database without
learning a query language. The most common form of output for any
database is a printed report.
How do relational databases organize and manipulate data? (pp. 526
532)
Relational databases operate by organizing data into various tables based on
logical groupings. Because not all of the data in a relational database is stored
in the same table, a methodology must be implemented to link data between
tables. In relational databases, the links between tables that define how the
data is related are referred to as relationships. To establish a relationship
between two tables, both tables must have a common field (or column). Once
linked, information can be drawn from multiple tables through the use of
queries (for onscreen viewing of data) or report generators (used to produce
printed reports).
What are data warehouses and data marts, and how are they used? (pp.
532 536)
A data warehouse is a large-scale electronic repository of data that contains
and organizes in one place all the relevant data related to an organization.
Data warehouses often contain information from multiple databases.
Because it can be difficult to find information in a large data warehouse,
small slices of the data warehouse called data marts are often created. The
information in data marts pertains to a single department within the
organization, for example. Data warehouses and data marts consolidate
information from a wide variety of sources to provide comprehensive
pictures of operations or transactions within a business.
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